The present invention relates to a pressure control mechanism for a piston pump which is particularly applicable to, but not necessarily limited to hydraulically operated steering systems.
In general, the discharge pressure of a piston pump is limited by a normally closed valve that opens in response to an upper limiting pressure to drain pressurized fluid from the pressure outlet of the pump into a fluid intake conduit connecting the pump to a low pressure region such as a fluid reservoir tank. The pressure limiting valve may be of a pressure relief jet type or of a storage pressure, charge type. Such a pressure control arrangement is particularly suited for a piston pump of the radial type having an adjustable flow restrictor in the intake conduit that restricts inflow to the pump by a variable amount whenever fluid is conducted thereto by the pressure limiting valve from the discharge outlet of the pump.
Pressure control mechanisms of the foregoing type wherein the inflow of the fluid to the pump intake is controlled, have the advantage of conserving energy to an extent not possible with those systems wherein flow of high pressure fluid is restricted. It is therefore an important object of the present invention to provide an economical pressure control system having a high degree of operational reliability and the energy conserving attributes of restrictively adjusting intake flow to the pump from a low pressure region to effect pressure control.